Treasury Secretary Steve Mnuchin asked if he could use a military plane on his honeymoon in Europe last month, although the request was eventually withdrawn.

Speaking at an event held by Politico, Mnuchin said Thursday that the request for a government airplane for travel to his honeymoon "was purely about alternatives of how I'd be able to be involved for national security" and his ability to use a "portable office" with secure connections to speak with other cabinet members, as well as the president.

"At the time, my staff wanted to make sure that I was – constantly had access to secure communication and secure information," he said. "This was one of the things we explored. So they put in a request to consider the use of an aircraft."

President Trump said he was unaware Mnuchin has made the request -- "it could be that he used a plane and he's paying for it. I don't know anything about it. I really don't," he told reporters on Air Force One on the way back from Florida Thursday. But he said he had complete confidence in Mnuchin, whom he called "a straight shooter."

A Treasury spokesperson said earlier Thursday that the request for military transportation was related to Mnuchin's official duties.

"The Secretary is a member of the National Security Council and has responsibility for the Office of Terrorism and Financial Intelligence," the spokesperson told CBS News. "We have multiple issues around the world where the Secretary is directly involved in national security, notably North Korea, Iran, and Venezuela, among others.

It is imperative that he have access to secure communications, and it is our practice to consider a wide range of options to ensure he has these capabilities during his travel, including the possible use of military aircraft. Treasury withdrew its request after a secure communications option was identified during the Secretary's extended travel."

Mnuchin, who was criticized for traveling aboard a government jet with his wife last month in order to view the solar eclipse, was married in June. Their honeymoon took them around the Mediterranean.